The invention relates to a device for improving the combustion efficiency of furnaces by controlling the flow of exhaust gases from the flue.
It is known that the efficiency of hydrocarbon fueled combustion furnaces is reduced through the loss of incompletely-combusted gases and heat up the exhaust flue of the furnace. It is further known that the efficiency of the furnace may be improved by interrupting the flow of exhaust gases from the furnace, thus causing the exhaust gases to dwell longer in the furnace and be more completely combusted. For example, U.S. Pat. No. 4,291,671 issued Sep. 29, 1981 to Senne discloses a baffle plate which is inserted into the path of the exhaust gases, causing eddy currents to be created and increasing the resistance to flow of the exhaust gases, thereby improving combustion efficiency in the furnace.
At the same time there are practical restrictions on the extent to which the exhaust gas flow may be restricted. Overly restricting the flow of exhaust gases may cause a high pressure build-up of combustible gases in the furnace which increases the risk of explosion. Consequently authorities have regulated the extent to which devices may restrict the exhaust flow. Such devices, however, in the past have not been readily adjustable to increase or decrease the amount by which the device restricts the exhaust gas flow.
Helical radiators have also been utilized in the flues of stoves or chimneys to increase the heat transfer between the exhaust gases and the stove pipe and thus increase the radiation of the heat to the room to be heated. An example of such a radiator is shown in U.S. Pat. No. 799,120 issued Sep. 12, 1905 to Way. Such radiators, however, have not been designed for modern gas furnaces and would be overly restrictive and dangerous if used in modern furnaces.